Unilateral transmission circuits



Feb. 17, 1959 .1. c. HOADLEY ET AL 7 UNILATERAL TRANSMISSION CIRCUITS Filed Feb. 21, 1946 2 Sheets-Sheet 1 4AAAAAAAAAL vvvvvvvvv AAA vvvvv ammo r03 J.CARL|SLE HOADLEY, DAVID 0. MC COY Feb. 17, 1959 Filed Feb. 21, 1946 .-I. c. HOADLEY ET AL, 2,874,287

UNILATERAL TRANSMISSION CIRCUITS 2 Sheets-Sheet 2 Elma/rm,

J. CARLISLE HOADLEY, DAVID 0. MC COY' UNILATERAL TRANSMISSION CIRCUITS James Carlisle Hoadley, West Newton, Mass., and

' David 0. McCoy, Washington, D. C.

This invention relates to unilateral transmission circuits, and is directed to the problem of obtaining sharp cut-E operation of a device of this character.

As is well known, unilateral transmission circuits are employed in many uses, but particularly in detector stages of amplitude modulated radio frequency receivers. They are also employed in impulse generator circuits for the purpose of clipping the overshoot of an impulse having predominantly one polarity, but being in part of the opposite polarity.

Previously suggested circuits are subject to considerable inefficiency in that they do not have a sharp cut-off point, and transmit small inverse voltages. That is disadvantageous in that the inverse conduction proportionately cuts down the rectifying or detection efficiency and it also renders it impossible to obtain unipotential impulses by clipping operation. In these respects, the circuit of the present invention offers greatly improved performance.

Accordingly, an object of the present invention is to provide an improved unilateral transmission circuit.

It is another object of the invention to generate uni-.

polar impulses.

tothedrawings, in which:

. Fig. 1 shows in circuit diagram an embodiment of the invention, 1

Fig.2 shows in circuit diagram another embodiment of the invention, 1

Fig. 3 shows, in circuit diagram, an impulse generator of the invention, and

Fig. 4 shows voltage waveforms present during operation of the circuit of Fig. 3.

The circuit of Fig. 1 constitutes a unilateral transmission network comprising a cathode follower tube 1 having anode 2 directly connected to a positive potential source 3, cathode 4 returned to ground through cathode impedance 5 and a control electrode 6. The control electrode is fed from input terminal 7 through condenser 8 and is returned to ground through resistor 10.

The cathode follower tube 1 has connected across it a second tube 11, with anode 12, control electrode 13, and cathode 14. Anodes 2 and 12 are connected together as are cathodes 4 and 14. Control electrode 13 is directly returned to ground. The output signal is developed across cathode impedance 5 and is delivered at terminals 15.

The operation of the circuit to clip the negative portion of a signal imposed on grid 6 is accomplished through the joint action of tubes 1 and 11. The signal is introduced into the input channel at terminal 7. In the absence of an input signal the two tubes draw suflicient current to develop small constant bias across cathode impedance 5. In this condition, tube 11 is operating under the bias developed across impedance 5, and tube 1 is carrying very slightly less current due to bias set up by flow through grid resistor of electrons intercepted by grid 6. The difference in steady state conditions in the two tubes is of only secondary importance, as

of Fig. 2, wherein the operating conditions may be identical.

Upon application of a positive voltage to grid 6, cathode 4 follows the grid potential, and the output channel fed by cathode impedance 5 delivers the positive waveform to terminal 15. During the rise in cathode potential, tube 11 is cut-off by the bias developed between its cathode 14 and grounded grid 13.

Upon introduction of a negative input signal to grid 6, the grid is driven below its average potential and consequently tends to drive cathode 4 toward ground. How ever, this is simultaneously opposed by the action in tube 11, where the drop in cathode potential is effective as a positive signal on grid 13 in relation to cathode 14. Consequently the inverse output voltage which otherwise would accompany cut-off in tube 1 is avoided by the increase conduction of tube 11 to maintain substantially the quiescent current value in cathode impedance 5.

It is apparent that the unilateral characteristics of the circuit of Fig. l are of equal utility in connection with a carrier modulated by a recurrent sine wave or speech signal, for instance, and with impulse signals having negative overshoots to be eliminated. The circuit of Fig. 2 is provided with dual input channels and has primary utility for clipping two series of impulses. The circuit also has other applications and may be employed as a mixer as well as a clipper, where signals are simultaneously present on the two control grids.

The circuit of Fig. 2 resembles that of Fig. 1 with the exception that grid 13 of tube 11 is returned to ground through impedance 16 instead of having a direct return. The operation of the circuit with respect of a recurrent waveform or a bipolar impulse applied to grid 6 of tube 1 is substantially identical with the circuit of Fig. 1. Due to the high impedance of the grid return of tube 11, however, this grid may also be used as a unilateral input channel. Under this mode of operation the functions of the tubes are reversed when grid 13 is used as an input grid. By employing the circuit of Fig. 2 therefore, two

decoupled unilateral input channels are made available,

both feeding the same output channel.

In Figure 3 is shown diagrammatically a unipolar impulse generator employing special characteristics of the transmission circuit.

The impulse generator comprises circuit components operative to supply in a pair of output channels two synchronous impulses of opposite predominate polarity followed by an inverse overshoot. The output channels are fed to a circuit such as is illustrated in Figure 2, which delivers an output signal substantially free of overshoot. The signals applied to the transmission circuit of Figure 2 are derived from a pair of tubes arranged for alternate conduction. In the circuit of Figure 3, these are shown as tubes 20 and 21. Only one of these tubes is conductive at a time, and the alternate conduction is continuously interchanged between the tubes to generate a recurrent series of output signals. Recurrent alternate conduction is effected by coupling tubes 20 and 21 in a free running multivibrator circuit. For this purpose anode 22 of tube 20 is connected through coupling condenser 23 to control grid 24 of tube 21. Anode 25 of tube 21 is reversely coupled through condenser 26 to control grid 27 of tube 20.

The output wave form of the multivibrator circuit shown is asymmetrical, and the time constant on control grid 24, of tube 21 is considerably shorter than that of the control grid in tube 26. For this purpose the resistance-capacity time constant of condenser 23 and return resistor 27 of grid 24 is less than the time constant of condenser 26 and resistor 28. Resistor 27 is variable Patented Feb. 17, 1959 in order to eflect desired control of the spacing of the output pulses.

The variation in potential produced at anode of tube 21 is shown at a in Figure 4. The Waveform present at anode 22 of tube 20 is shown at b in Figure 4. In the circuit of Figure 3, the output signal derived from the alternately conducting tubes are obtained from their anode. The anode signals are differentiated in the grid circuit of a second pair of tubes, and 31. Tubes 30 and 31 are arranged as separate cathode followers. Control grid 32 of tube 30 'is returned to ground through resistor 33 and is coupled to anode 22 of tube 20 through condenser 34. The resistance capacity time constant of control grid 32 is made very small in order to obtain the derivative of the anode signal shown at d in Figure 4. This results in a variation of the control grid potential of tube 30 as shown at a in Figure 4.

Similarly, control grid 35 of cathode follower tube 31 is returned to ground through resistor 36, and is driven from anode 25 of tube 21 through coupling condenser 37. The time constant of condenser 37 and resistor 36 is selected to obtain a derivative waveform as shown at c in Figure 4.

The output signals from tube 31 and 31 are obtained from the cathode resistors 38 and 39 respectively. These signals are of the same waveform as the signals introduced on the control grid of these tubes and shown at d and c in Figure 4 respectively.

The output signals from tubes 30 and 31 are applied to the input channels of the transmission network corresponding to that described in connection with Figure 2 of the drawing. In the signal generator shown, these tubes comprise triodes 40 and 41. Anodes 42 and 43 of tubes 40 and 41 are returned to a source of positive potential 44. Cathodes 45 and 46 are returned to ground through common cathode resistor 47. Control grid 48 of tube 40 is returned to ground through resistor 49, and is driven through coupling capacitor 59 from the cathode load impedance of tube 30.

Control grid 51 of tube 41 is returned to ground through resistor 52, and is coupled to the cathode load resistor of tube 31 through condenser 53. The control potentials applied to the grid of tubes 40 and 41 are of the waveform shown at d and c in Figure 4 respectively.

The operation of the circuit of Figure 2 under these input signals supplies successive positive output impulses free of inverse overshoot from common cathode resistor 47.

The simultaneous application of large amplitude impulses of opposite polarity to control grids 48 and 51 drives one tube to a conduction level substantially to cut-off, the grid potential of that tube being well below the cut-off value. Simultaneously the other tube is driven to a high conductive level. The cathode follower action of the tube receiving the positive grid signal completely overrides the other tube which is driven to cutoff and consequently the output channel supplies a positive impulse from cathode resistor 47.

1 as shown at e in Figure 4, are substantially free of inverse overshoot. I

It will be understood that the embodimentsof the invention disclosed are exemplary only, and that the limits thereof are to be ascertained from the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. A unipolar impulse generator comprising a first pair of tubes, means coupling said tubes for alternate conduction, means differentiating the output signal of each tube, a second pair of tubes each having a cathode and a control grid, a common cathode load impedance for said second pair of tubes, means applying the differentiated output of one of said first pair of tubes to one control grid and the differentiated output of the other of said first pair of tubes to the other control grid, and an output channel fed from the cathode lead impedance.

2. In a unilateral transmission circuit, a first electron tube and a second electron tube, eachhaving at least an anode, a cathode and a control element, means connecting the anode of said first electron tube to the anode of said second electron tube, means connecting the cathode of said first electron tube to the cathode of said second electron tube, a source of potential having a first terminal at a positive potential and a second terminal at a constant negative potential relative to a se lected potential level, means connecting the anode of said first electron tube to said first terminal, an impedance element, means for connecting said impedance'element between the cathode of said first electron tube and said second terminal, means connected to the control element of said second electron tube for maintaining said control element at a potential equal to the potential of said sec end terminal, a source of signals, means for connecting said source of signals to the control element of said first electron tube, an output circuit, and means for connecting said output circuit across said impedance element.

References Cited in the file of this patent UNITED STATES PATENTS 2,252,613 Bingley Aug. 12,

2,276,565 Crosby Mar. 17, 1942 2,405,876 Crosby Aug. 13, 1946 2,418,127 Labin Apr. 1, 1947 2,452,549 Cleeton Nov. 2, 1948 2,485,665 Shepherd Oct. 25, 1949 

